Gasphase ion source for time-of-flight mass-spectrometers with high mass resolution and large mass range

Abstract

To achieve a high mass resolution in a time-of-flight mass-spectrometer with gasphase ion source, the initial velocity components in the direction of acceleration of the ion source must be kept small. This can be done by injection the analyte gas or ion beam at right angles to the direction of acceleration into the ion source. When the direction of acceleration and the direction of the analyte gas or ion beam or not colinear, the amount of unwanted gas ballast in the drift space of the time-of-flight mass-spectrometer will be less. This will increase the dynamic range of the mass-spectrometer. The heavier an ion is, the more its path will deviate from the axis of the ion source and if it deviates too far from the axis of the ion source it will be lost. This effect gives the limit of the mass range of such an ion source. If the electrical deflection field for these ions is already within the acceleration region of the ion source, its mass range can significantly be enlarged.

I claim: 
     
       1. A gasphase ion source from within which ions are started on their path into time-of-flight mass-spectrometers, in which the analyte gas or ion beam (10) has a velocity component normal to the direction of acceleration in the ion source,   in which is defined a region of space called extraction volume (11), said region containing ions at start-time of mass-analysis, the mass of said ions being determined by measuring their time-of-flight, with   electrodes (1,2) for defining an acceleration field, and   electrodes (20,25) for generating a transverse electric field, that can be used to change transverse velocity components of charged particles   characterized by a geometrically continuous region of space, in which the accelerating and transverse fields are superposed, said region of space containing the extraction volume (11).   
     
     
       2. A gasphase ion source for time-of-flight mass-spectrometers according to claim 1, characterized by electrodes (20,25) capable of generating a transverse field, said electrodes being arranged within the acceleration field. 
     
     
       3. A gasphase ion source for time-of-flight mass-spectrometers according to claim 2, characterized by electrodes (20,25) capable of generating a transverse field, said electrodes being arranged between the electrodes (1,2) that generate the acceleration field. 
     
     
       4. A gasphase ion source for time-of-flight mass-spectrometers according to claim 1, characterized by electrodes (20,25) capable of generating a transverse field, said electrodes having for the main part rotationally symmetric form around the axis pointing in the direction of acceleration of said ion source,   said electrodes being split along a plane (B--B') into two symmetric half-parts, said plane being normal to the direction of flight of the analyte gas or ion beam.   
     
     
       5. A gasphase ion source for time-of-flight mass-spectrometers according to claim 1, characterized by electrodes (1,2) for generating the acceleration field and electrodes (20,25) for generating the transverse field, all said electrodes having constant voltages. 
     
     
       6. A gasphase ion source for time-of-flight mass-spectrometers according to claim 1, characterized by electrodes (1,2) for generating the acceleration field and electrodes (20,25) for generating the transverse field, one or several of said electrodes having constant voltages and one or several of said electrodes having time-dependent voltages. 
     
     
       7. A gasphase ion source for time-of-flight mass-spectrometers according to claim 1, characterized by electrodes (1,2) for generating the acceleration field and electrodes (20,25) for generating the transverse field, all said electrodes having time-dependent voltages. 
     
     
       8. A gasphase ion source for time-of-flight mass-spectrometers according to claim 1, characterized by electrodes (20,25) defining a transverse electrical field, said electrodes being additionally split symmetrically along a plane, said plane being defined by two vectors, one of said vectors being the direction of the analyte gas or ion beam, the other of said vectors being the direction of acceleration in the ion source. 
     
     
       9. A gasphase ion source for time-of-flight mass-spectrometers according to claim 1, characterized by electrodes (1,2), one or several of said electrodes representing a boundary between regions of different gas pressure within the time-off-light mass-spectrometer, and gas flow restrictions (3) that are integrated into said electrodes.